Coagulation is a complex process by which blood or blood plasma forms clots. It is an important part of homeostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel. Since inadequate coagulation can lead to an increased risk of bleeding (hemorrhage) and excessive coagulation can lead to obstructive clotting (thrombosis), the coagulation process is tightly controlled and highly conserved throughout biology.
Blood coagulation disorders are very dangerous, and the therapeutic means to treat them and to control coagulation are difficult to manage and also dangerous. In addition, many patients are chronically treated with anticoagulant drugs such as warfarin after receiving replacement heart valves and need to be monitored. It is increasingly advantageous to be able to monitor coagulation parameters, in particular prothrombin time (“PT”; also expressed as the mathematical transform, International Normalized Ratio “INR”) and Activated Partial Thromboplastin Time (“aPTT”) as part of a more comprehensive health and therapy monitoring program in which biomarkers and other therapeutic agents are measured. PT, INR and aPTT can be measured in clinical laboratories using conventional methods requiring relatively large volumes of blood or plasma, typically 5 mL collected into fixed volume vacuum tubes. In order to improve monitoring of patient blood coagulation parameters, improvements in performing coagulation assays and measuring coagulation parameters are needed.